Tool holding collet for boring bar assemblies



Oct. 27, 1953 R. w. BOYD, JR 2,657,066

TOOL HOLDING COLLET FOR BORING BAR ASSEMBLIES Filed Dec. 22, 1950Patented Oct. 27, 1953 TOOL HOLDING COLLET FOR BORING BAR ASSEMBLIES RoyW. Boyd, Jr., Chicago, Ill. Application December 22, 1950, Serial No.202,322

1 Claim.

This invention relates to a boring bar and more particularly to a toolholder for a boring bar assembly.

The boring bar with which the present invention is concerned may betermed. a multiple boring bar assembly. In the conventional constructionthis type of boring bar contains a number of bores in which tool holdingcollets are positioned. Provisions are generally made for removing thecollets so that the tools may be removed from the collet for sharpening.Various adjusting devices have been provided on conventional boringbars, these adjustments being intended to permit the tool to be adjustedfor cornpensating for wear of the cutting point. It is a prime object ofthis invention to provide an proved type of boring bar assembly, theassembly including a novel tool holding collet which will permit theoperator to make ready and quick adjustments whenever necessary.

Still another object is to provide a collet for holding a cutting tool,the collet having provisions whereby the cutting tool may be adjustedrelative to the collet with a minimum effort on the part of theoperator.

Still another object is to provide a tool holding collet having a bodyportion provided with an outwardly threaded shank portion. The body islongitudinally slotted to provide a plurality of resilient fingers. Theouter surface of the fingers define a tapered or conical surface whichmay be readily inserted into the conical bore of a boring bar. A nutwhich is threaded over the threaded portion of the shank is adapted toengage the body of a boring bar in order to advance the colletlongitudinally with respect to the tapered bore to effect inwardclamping action of the resilient collet fingers which will rigidly clampa cutting tool held between said fingers. The shank portion of thecollet is provided with a threaded bore in which a thrust member or plugis threaded. The plug is adjustable within the threaded bore and isadapted to engage the cutting tool held between the resilient fingers inorder to move the tool longitudinally outwardly from the collet therebycompensating for wear of the cutting portion of the cutting "tool.

These and further objects will become more readily apparent upon areading of the specification when taken in connection with the accoznpanying sheets of drawings.

In the drawings:

Fig. l is a partial view of a boring bar assembly. The view havingportions broken away to show a pair of tool holding collets positionedin the operating position on the boring bar.

collet fingers 2d.

Fig. 2 is an exploded view of a tool holding collet and its associatedpart, the parts being arranged in position of their assembly withrespect to the tool holding collet which is shown in section.

Fig. 3 is a sectional view of a portion of a tool holding collet, theView being taken substantially along the line 33 of Fig. 1.

Fig. 4 is a bottom view of the tool holding collet.

Referring particularly to Figs. 1 and 2, a boring bar is generallydesignated by the reference character Ill. The boring bar I 0 comprises,essentially, a body H having a shank portion I2, the shank portion beingadapted to engage the chuck of a boring mill (not shown). The boring barIn is also provided at its forward end with a cutter head I3, only aportion of this head being shown since it forms no part of the presentinvention.

The boring bar 10 may generally be of conventional construction. Thetype of bar which is shown being a multiple cutting bar in thatprovisions are made to hold a number of tool holding collets. The toolholding collets which are shown assembled on the boring bar 10 varysomewhat in. size depending on the size of the tool which is held in thecollet. For the purpose of the present disclosure, the same referencecharacters will be applied to all of the collets shown since the sameessential elements and patentable features are present in all of thecollets.

The body I l of the boring bar Iii is provided with a plurality ofconical openings Hi. The openings M extend through the body H,v and asshown in Fig. 1, these openings It may he positioned at various anglesdepending on the out which is to be made. a i i The tool collet [5 withwhich the present invention is concerned consists generally of a body I!which is provided at one end with a shank portion 18. The shank portionis is extcriorally threaded. The body I! is longitudinally slotted toprovide a plurality of collet fingers 29. The collet fingers 2!] are ofa resilient construction and the outer surfaces of the collet fingers2!] are shaped to provide a tapered or conical surface 2!. The taperedor conical surface 2! is adapted to mate or to conform to the conicalbore l4 provided in the boring bar Ill.

As best indicated in Fig.1, a cutting tool is positioned or insertedbetween the resilient The cutting tool is provided with a suitablecutting edge or surface for oper ating upon the metal to be cut.Referring again to Fig. 2, the threaded shank I8 is provided with alongitudinally extending threaded bore 23 in which a stud 2c isthreaded. The stud 2% may so be considered as a thrust member andconsists of a tool holding recess 25 at one end and tool engagingprojection 25 at the other end, A nut 2'5 is threaded on the exteriorlythreaded surface of the shank l8.

In the use and assembly of the tool collet iii the following steps takeplace. As best shown in Fig. 2, when the collet fingers 29 are in therelaxed position they are rather widely flared and the cutting tool 22may be easily inserted between said fingers. Before the cutting tool 22,however, is inserted in between the collet fingers 23, the collet willbe placed in the conical bore Id of the boring bar It). Since theconical bore extends completely through the body ll, the shank E8 of thetool collet will project outwardly from one end of the bore id. Theadjusting stud 2 3 has been screwed into place within the threaded bore23. Theprojection it acts as an adjusting gauge and the threaded plug 25 is screwed to a position Within the bore 23 Whereupon the tool 22 isinserted between the fingers 2?.

After the tool 22 has been thus positioned between the fingers 20, a nut21 is screwed over the exteriorly threaded shank 18. The nut 2'! isscrewed to a position, as best shown in Fig. 1, wherein the nut 21engages a fiat shoulder surface 28 positioned adjacent the conical boreE l. As the nut 27 is tightened, the collet 55 will be movedlongitudinally into the bore [4. As the collet i5 is drawn further intothe bore M the fingers 2e are forced against the sides of the conicalbore i4 thereby forcing the fingers inwardly into tight grippingengagement with respect to the tool holder 22. It can now be seen thatthe cutting tool 22 is tightly held within the collet l5 and r on theboring bar ID.

The principal advantage of this novel collet design [5 is the ease ofadjusting the cutting tool 22 to compensate for wear of its cuttingpoint. As the cutting point wears away adjustment of the cutting tool ismade by simply inserting a wrench within the tool receiving recess orsocket and the stud 24 is turned. By rotating the stud 25 the cuttingtool 22 is advanced in a direction outwardly from the boring bar to thedesired projection for engagement with the work. After the cutting toolhas been thus advanced the wrench is removed and the operation of thetool may continue.

By this novel and easy construction, adjustment of the cutting tools mayquickly be made without time consuming operation. It can be appreciatedthat inmultiple boring bar assemblies wherein a variety of shapes andnumber of tool collets are utilized it is exceedingly desirable towithout departing from the spirit of the inven tion as shown, orthescope thereof as defined in the appended claim.

What is claimed is:

In a tool holder having a bar provided with a conical bore extendingsubstantially laterally through the bar, said bar having a shoulder portion concentric with said bore and recessed in the peripheral surface ofsaid bar a tool collet adapted to be secured within said bore, saidcollet including a shank and a hollow body ,'said shank having anexternally threaded portion and being provided with a threadedboreextending through said shanlgsaid body having an outer taperingsurface and being longitudinally split to provide resilient toolengaging collet fingers adapted to receive and clamp a tooltherebetween, a nut threaded on the externally threaded portion of theshank and seated in engagement with the shoulder portion, said nut beingrotatable with respect to-said shank for moving said colletlongitudinally within the bore of the tool holder whereby the colletfingers are moved inwardly for clamping a tool disposed between saidfingers, and a threaded thrust member disposedwithin the bore of saidshank, said thrust member having a tool receiving recessed portion atone end normally-disposed below the peripheral surface of said bar andbeing rotatable within the thread ed bore intoengagement with a toolsecured between the collet fingers whereby a tool may be longitudinallyadjusted with respect to said collet.

ROY W. BOYD, JR.

References Cited in the file of this patent UNITED STATES PATENTS

